Buggy code:
public class SingletonMap < K , V > implements Serializable , Cloneable , BoundedMap < K , V > , KeyValue < K , V > , OrderedMap < K , V > { private static final long serialVersionUID = - 8931271118676803261L ; private final K key ; private V value ; public SingletonMap ( ) { } public SingletonMap ( K key , V value ) { } public SingletonMap ( KeyValue < K , V > keyValue ) { } public SingletonMap ( Map . Entry < K , V > mapEntry ) { } public SingletonMap ( Map < K , V > map ) { } public K getKey ( ) { } public V getValue ( ) { } public V setValue ( V value ) { } public boolean isFull ( ) { } public int maxSize ( ) { } public V get ( Object key ) { } public int size ( ) { } public boolean isEmpty ( ) { } public boolean containsKey ( Object key ) { } public boolean containsValue ( Object value ) { } public V put ( K key , V value ) { } public void putAll ( Map < ? extends K , ? extends V > map ) { } public V remove ( Object key ) { } public void clear ( ) { } public Set < Map . Entry < K , V > > entrySet ( ) { } public Set < K > keySet ( ) { } public Collection < V > values ( ) { } public OrderedMapIterator < K , V > mapIterator ( ) { } public K firstKey ( ) { } public K lastKey ( ) { } public K nextKey ( K key ) { } public K previousKey ( K key ) { } protected boolean isEqualKey ( Object key ) { } protected boolean isEqualValue ( Object value ) { } static class SingletonMapIterator < K , V > implements OrderedMapIterator < K , V > , ResettableIterator < K > { private final SingletonMap < K , V > parent ; private boolean hasNext = true ; private boolean canGetSet = false ; SingletonMapIterator ( SingletonMap < K , V > parent ) { } public boolean hasNext ( ) { } public K next ( ) { } public boolean hasPrevious ( ) { } public K previous ( ) { } public void remove ( ) { } public K getKey ( ) { } public V getValue ( ) { } public V setValue ( V value ) { } public void reset ( ) { } public String toString ( ) { if ( hasNext ) { return "Iterator[]" ; } return ( ( ( "Iterator[" + ( getKey ( ) ) ) + "=" ) + ( getValue ( ) ) ) + "]" ; } } static class SingletonValues < V > extends AbstractSet < V > implements Serializable { private static final long serialVersionUID = - 3689524741863047872L ; private final SingletonMap < ? , V > parent ; SingletonValues ( SingletonMap < ? , V > parent ) { } public int size ( ) { } public boolean isEmpty ( ) { } public boolean contains ( Object object ) { } public void clear ( ) { } public Iterator < V > iterator ( ) { } } @ SuppressWarnings ( "unchecked" ) public SingletonMap < K , V > clone ( ) { } @ SuppressWarnings ( "unchecked" ) public boolean equals ( Object obj ) { } public int hashCode ( ) { } public String toString ( ) { <START_BUG> return new StringBuffer ( 128 ) . append ( '{' ) . append ( ( ( getKey ( ) ) == ( this ) ? "(this<seq2seq4repair_space>Map)" : getKey ( ) ) ) . append ( '=' ) . append ( ( ( getValue ( ) ) == ( this ) ? "(this<seq2seq4repair_space>Map)" : getValue ( ) ) ) . append ( '}' ) . toString ( ) ; <END_BUG> } }

Fix:
return new StringBuilder ( 128 ) . append ( '{' ) . append ( ( ( getKey ( ) ) == ( this ) ? "(this<seq2seq4repair_space>Map)" : getKey ( ) ) ) . append ( '=' ) . append ( ( ( getValue ( ) ) == ( this ) ? "(this<seq2seq4repair_space>Map)" : getValue ( ) ) ) . append ( '}' ) . toString ( ) ;